1. Field of the Invention
The present invention generally relates to a hollow fiber carbon membrane comprising a polyphenylene oxide derivative, and method for production thereof, in particular, to a hollow fiber carbon membrane comprising a polyphenylene oxide derivative which has excellent gas separation performance, improved brittleness and excellent unbreakable flexibility, and method for production thereof.
2. Description of Related Art
Carbon membranes have exhibited excellent gas separation performance in various inorganic membrane applications, and can also be used in the environments requiring heat resistance and chemical resistance where organic membranes are unable to be used, thus their practical applications have been highly expected. In addition, due to excellent pressure resistance and larger membrane area per unit volume, hollow fiber membranes can be made into more compact separation membrane modules, as compared to flat membranes or spiral membranes. However, in making the separation membrane modules, there are disadvantages such as poor brittleness, difficult to be sealed and high cost for the hollow fiber membranes made up of the carbon membranes.
To date, cellulose-based carbon membranes have been known as carbon membrane with excellent flexibility and bending strength, but this kind of carbon membrane has several problems, such as relatively more and complicated preparation steps (see patent reference 1). Additionally, it has been reported that an asymmetric hollow fiber membrane comprising an aromatic polyimide is partially carbonized to obtain a carbon membrane with excellent flexibility and bending strength, but this carbon membrane cannot satisfy the cost requirement, and the preparation of the polymer material is very complex (see patent reference 2).
The present inventor has filed a patent for a hollow fiber carbon membrane comprising an inexpensive polyphenylene oxide derivative, and a carbonized membrane for gas separation with excellent formability, gas separation performance and gas permeability has been obtained (see patent reference 3).    Patent reference 1: Japanese Patent No. 2914972.    Patent reference 2: Japanese Patent No. 2673846.    Patent reference 3: Japanese Patent Publication No. 2006-231095.
However, further researches by the present inventors have indicated that the hollow fiber carbon membrane obtained by utilizing the method described in the patent reference 3 has poor brittleness and is easily broken in various operations.
Therefore, there still remains a need in the art for a hollow fiber carbon membrane with excellent gas separation performance and high unbreakable flexibility which can be obtained from inexpensive materials by simple steps.